


Welcome to Britannia

by eloquated



Category: Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: Alternate Universe - Historical, Celtic!Mycroft, Fluff and Humor, Gen, M/M, Mycroft Being a Good Brother, Pre-Slash, Roman!Greg, not historically accurate
Language: English
Status: Completed
Published: 2020-11-20
Updated: 2020-11-20
Packaged: 2021-03-10 03:49:25
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,717
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27647083
Author URL: https://archiveofourown.org/users/eloquated/pseuds/eloquated
Summary: Everyone knew Britannia was just a stain on the edge of the empire.  A miserable, cold little blot on the map.So naturally, that's where the formerly glorious IV Augustus, and Gregorius Lestradus, had been sent.Maybe a chance meeting with a Celtic noble can convince him that it's not so bad!
Relationships: Mycroft Holmes & Greg Lestrade, Mycroft Holmes & Sherlock Holmes, Mycroft Holmes/Greg Lestrade
Comments: 17
Kudos: 63





	Welcome to Britannia

**Author's Note:**

  * For [TheArtStudentYouHate](https://archiveofourown.org/users/TheArtStudentYouHate/gifts), [janto321 (FaceofMer)](https://archiveofourown.org/users/FaceofMer/gifts).



> Hey everyone! This is just a funny little thing that popped into my head while watching Rotten Romans!
> 
> Dedicated to the wonderful people who "subtly" mentioned that they loved the idea of a Celtic Mycroft. This is all your fault! ❤️

"Come to Britiannia, they said. Stay in the glorious Roman army and see the world, they said. 'Course, they didn't say anything at all about the bloody rain, or the mud, or the cold. And they definitely couldn't be bothered to tell us that we'd end up spending most of our time putting in the underfloor heating for the Legates. Like we've got nothing better to do than manual labour! And don't even get me started on the food! If I never see another parsnip, it'll be too soon. And these bloody nettles!"

Oh, it was all well and good to be a Centurion in Rome. Or even haring around Greece, or Hispania, killing and looting and expanding the Empire. 

Not that Greg was a Centurion. Not yet. Not until Minicius Bonus died, or finally gave him the promotion he deserved.

But this? Basket under his arm like some kind of peasant woman? This was just a bit embarrassing! 

And worse, because after two hours scouring the countryside, Greg still hadn't managed to find more than a few wilted, sad little leaves that he wasn't entirely sure were nettles at all. It was cold, and getting dark, and whoever had designed his cloak had clearly never intended to keep out anything more uncomfortable than a warm, summer breeze off the Bay of Neapolis!

Trudging along in the gloomy twilight, Lucius Gregorius Lestradus fervently wished for two things:

First, to be back in Rome. The sooner the better.

And second, that he hadn't lost the path back to camp.

**Ω**

"Find your little brother, Maël Ceallachán. You know he has high spirits and just wants to indulge his curiousity. As if I have nothing more important to do with my time than to make sure he doesn't get himself eaten by wolves, or stuck in a bog. Honestly, I have enough work with the tribe in shambles, the last thing I need is for him to go wandering off!"

Much less wandering off in the middle of the night. "It'd serve him right if he followed the will'o'wisps to a bad end." He muttered resignedly to himself. 

Five years earlier, the Iceni had been powerful; led by his aunt Boudicca, they'd almost managed to drive the whole Roman army out of their country. But of course, it hadn't been that easy. And the Romans had...

Well, they hadn't been smarter. Mycroft was very sure of that. Bunch of barbarians, with their frilly, fringed skirts and sandals. What sort of idiots wore sandals in this climate? There was snow! It would serve them right if they all got chilblains and frostbite, and had their toes fall off before they fled back to Rome.

It was a pleasant image, but it wasn't going to help him find his little brother. 

The sun had already set beyond the horizon, and the moon was thin and pale, like a mocking smile overhead.

Useless. 

**Ω**

There were few things in the Jupiter-cursed world worse than being lost in the moors of Britannia after dark. In fact, Greg would happily bet his last sesterce that there was  _ nothing  _ worse.

Except for maybe being stuck in one of the gladiatorial arenas-- but at least then he'd be warm!

He wasn't entirely sure how long he'd been wandering around in the dark, up one hill and down another, heading in the vague direction of camp. Of course, the problem with all hills looking alike, was that he was no longer sure which way that was. Or any way, in fact. For all he knew, he could be half a foot away from tumbling into one of those damned bogs. Or a river.

The old crone that had sent him to find the nettles was going to have a lot to answer for when he got back!

Everything seemed quite dire, until he heard the sound of a voice not far ahead. Well, it wasn't really ahead; it was mostly to the left, and forward a little, but the more important part was that he wasn't alone.

And that the man hadn't seemed to notice him.

As silently as he could in a breastplate, Greg crept along, his shoulders hunched and all but crawling through the short, scrubby grass. It's all that seemed to grow in this bloody country; had they never heard of the sun? Or vineyards?

The adventurous part of being in the army was much more fun when you had company, and weren't half frozen.

Even in the dark, Greg could see the bright flash of the man's red hair. He wasn't particularly old; probably a little younger than Greg himself, if he had to wager a guess. And he was bundled up from ears to toes in a heavy fur cloak that looked a damn sight warmer than Greg's woolen one.

Though it didn't look as nicely tanned as Roman leather would be. He couldn't really blame the man, though-- everyone knew that Roman craftsmen were the undisputed best in the world.

He was also most definitely a man. Long haired, with those beaded braids the Celts seemed to favour, and obviously skinny beneath that cloak; but a man all the same.

A captive Celt would be a useful prize! 

But more importantly? A Celt might just know his way to the Roman camp.

**Ω**

"Seachnaslach--  _ Seachnaslach! _ Where are you?"

Mycroft sighed for what felt like the dozenth time, and prodded the spongy ground in front of him with the end of his walking stick. The sigh did nothing to expel the tight, nervous knot in his chest. His brother had gone missing before, more than once, but he'd never ventured this far from the tribe.

What if something had happened to him? 

What if he'd been eaten? Or hurt? Or captured by those Romans that had set up camp near the ridge?

Annoyance had long since melted into fear, staring into the darkness with his eyes and ears keened for any sign of his brother. It was late, and his mother was going to kill them both if he didn't find him soon.

"Seachnas-- _ oof! _ "

With a hard thud, something leaped at Mycroft from behind, sending them both careening down the side of the hill. His lungs burned as they tumbled-- and it definitely wasn't a wolf, because they were smarter than whoever had tackled him.

Probably a Roman.

They both reached the bottom of the hill with a bump, breathing hard, the man draped across Mycroft's chest like some a big, stupid weight. 

"What were you thinking?!" He exclaimed, pushing back against the man's shoulder in a vain attempt to dislodge him.

Instead, the man (and, yes, a Roman. He could tell by the close-cropped hair, and the dark eyes) grabbed his shoulders and pinned him down to the cold, wet dirt. 

Well, this was inconvenient. He had better things to do with his life than be manhandled by Romans!

"Unhand me, and I may let you live!"

**Ω**

In retrospect, Greg thought it might have been a minor oversight that he didn't speak the Celtic tongue. It was fast, and clipped, and would have been strangely pretty, if his head wasn't throbbing from the long, ungainly fall down the hill.

It was probably also an oversight that he hadn't seen the hill. 

But in his own defense, (since he doubted the savage was going to give him much quarter, no matter how pretty his blue eyes were) it was very dark. 

"Right... Hold still! I'm not letting you up!" He muttered under his breath, and shifted a little in an attempt to free his knee from the rather intimate place between the Celt's thighs where it had twisted in their landing. "Would you just... Look, I'm trying to..."

"Your cape is stuck under my shoulder. If you'd stop wriggling, I might be able to untangle us."

Greg blinked down at the man, who was giving him an unflattering look.

This close, he could see the pale Celtic gold strung through the man's ear lobes, and the tiny beads strung through his red hair. He was furious, mouth pinched; but his cheeks were flushed from cold, and exertion and anger, and Greg was suddenly very aware of how close they were.

"Could you?" He retorted, sounding more petulant than he wanted. But he didn't want to stay trapped on the ground by his cloak (and it was a cloak, not a cape!) any longer than he had to, so he stilled.

"Is this what all Romans do? Hide in the dark and jump out at people? It doesn't sound like much of a tactic. Unless you're eager to inadvertently dash out your brains on a rock." 

The man's Latin was very good, rolling across his lips with a soft strangeness in his accent that made Greg want to listen. It was fascinating, the sounds of his country in the mouth of this savage, red-haired man.

With a bit of adjusting, they managed to scramble to their feet, apart. Greg reached for his sword, only to discover that it had tumbled from its' sheath, and was halfway up the incline. 

Not far from the other man's walking stick.

He eyed the Celt.

Who eyed him back.

"I won't kill you, if you don't try to kill me."

"Forgive me, but I find that a little hard to believe, given that you're the one who attacked me unprovoked." 

Greg grunted faintly, the man did have a point. "I'm trying to find my way back to camp, and I thought you might be able to help me." It sounded more polite than admitting that he'd planned to take him captive in the process. 

It wasn't anything personal. Only, his people were suffering in this blasted Britannic weather, and so far, the Celts they'd captured hadn't been very forthcoming with help.

Not that Greg really blamed them, they couldn't help being less civilized-- that bitch Boudicca had proven that. But it would have made everything so much easier! It wasn't as though they'd come to cause trouble, they were here to civilize them. To bring them sanitation, and roads, and medicine.

To improve their lives! 

The man crossed his arms beneath his cloak, and eyed Greg like he was covered in something unpleasant, and possibly smelly. "I'm afraid I don't have time to play tour guide tonight. I have to find my..." He paused half a beat, motioning to his side as he obviously tried to summon the right words. " _ Parvus frater,  _ I believe you would say. My little brother."

Greg stopped and tilted his aching head. That changed things, "It's no place for a boy to be out alone." He ventured, and nodded towards the Celt as he started to trudge back up the hill, "You've got all sorts of nasty beasts here."

"Yes, I was aware. Thus, my attempts to find him."

"Right, yeah..." Out in the darkness they could hear the sound of wolves, their howls bringing up goosebumps on Greg's arms and legs. "How about a truce?" He offered impulsively, "I'll help you find him, and you show me back to my camp?"

There was a pause, one of the Celt's pale eyebrows raised skeptically, "Why would you do that?"

"Because I'm not a barbarian? And you said it was a kid. Out here. Alone." Greg frowned; what did this bloody Celt take him for?

"I... Suppose. That would be acceptable. Do you have a name?"

Greg grinned, and held out his hand with a game flourish, "Gregorius Lestradus, but you can call me Greg. Everyone does." If he was going to help the man, he might as well be nice about it! And it would be easier than referring to him as 'the Celt'.

Who eyed his offered hand for a few resigned seconds, before clasping his wrist formally, "Maël Ceallachán."

Greg blinked, "Myl... Mile... Mile'calli... Sorry, mate, run that by me again?"

"Maël Ceall-- most of your people call me Mycroft, it seems to be easier for you Romans to say."

And faster, Greg supposed, than trying to break down the musical string of incomprehensible sounds into something he could repeat, hopefully without mangling.

"Mycroft... Yeah, I can do that."

**Ω**

Four eyes would probably be better than two, Mycroft allowed himself to think. Even if he had his doubts that eyes as dark as Greg's could be useful at night. Technically, he supposed, they could be made for the night; but without an experiment, he couldn't be sure.

His doubts only increased when he saw the Roman-- Greg-- retrieve a basket from the top of the hill.

"Why are you carrying old dandelion greens?"

"These aren't dandelions! Those are yellow." Greg scoffed, but looked down at the basket with much less confidence than he'd sounded. "Aren't they? I thought these were nettles." He had the good grace to look a bit sheepish as he poked through the wilted, saw-edged leaves with the tip of his finger.

Mycroft hadn't expected to laugh. In truth, he couldn't remember the last time he had. In the wake of the rebellion, and his aunt's death, the world had seemed like a much more complicated place. 

His parents were doing their best, but the sheer fact that he was out here, in the middle of the night, with a strange Roman, and looking for his little brother? Well, it was fairly damning commentary. Once upon a time his tribe had been respected.

Now they were decimated, lost in the lands that had always been theirs.

"Nettles are shorter, with less pronounced ridges." Mycroft supplied after a long, considering pause, "And dandelions are only yellow at the start of summer. Don't Romans know anything about botany?"

It felt like a very small win when Greg scrunched up his nose, and emptied his basket onto the ground. "I'm a soldier, I don't need plants. And what does a savage know about science?"

Mycroft crossed his arms beneath his cloak, his walking still gripped tightly in one hand. He refused to admit that the Romans had brought some fascinating new technology; the baths, in particular, were something he'd been trying to convince his tribe to adopt for what felt like an eternity. 

Mycroft: 1.

Unfortunately, the Roman had scored a point, too.

"I know enough. And we're supposed to be looking for my brother."

Greg nodded, and turned to look out into the darkness, a furrow forming between his brows. "Is he going to be scared out here alone? My brothers would be." He felt strangely glad to know that they were safely back in Rome, still dreaming of the adventures they'd have when it was their turn in the military.

Mycroft smirked, faint and worried, and shook his head, "Seachnaslach would ask the Morrigan to borrow their eye, if given the opportunity. He's curious about everything. Especially things he shouldn't be curious about. It's quite trying, in fact."

They lapsed into a quiet that lasted for half a mile, until Greg looked over and asked, "So, what's a Morrigan?"

The explanation led into a conversation about Celtic beliefs, which Greg thought were fascinating; and Roman myths, which made Mycroft blush. By the time the first light of dawn was streaming over the craggy moor, they'd covered Roman maths, and Celtic language, and decided that little brothers were a trial, no matter where you were from.

Greg's voice was pleasant, easy to listen to. It was also the only thing that staved off the raw panic building in Mycroft's chest. Trouble he might be, but where was Seachnaslach?

And at dawn he walked Greg back to the Roman army camp, their pennants flapping in the cold morning air. 

"I'll keep an eye out for him, yeah? Maybe one of the patrols saw something." Greg rubbed the back of his neck as they stood out of sight of the guards at the wall. "And if he's half as smart as you, he'll be alright. Might even be back home already."

Mycroft chanced a weak smile and nodded, "Perhaps."

**Ω**

As luck would have it, the boy had been found the night before, skulking around camp and trying to catch sight of the soldiers inside. He'd already made something of a name for himself, with his quick tongue and easy Latin-- but it was passed midday by the time Greg was able to sneak down to the makeshift cell he was being held in.

"So, you're Seach..nas...lach." Greg greeted him, both arms crossed over his breastplate.

"And you're butchering my name. If you're not going to say it properly, you may call me Sherlock. You ought to be able to manage that with some small degree of success."

Whatever Greg had expected, it wasn't this tousle haired little mite. Sherlock-- because it was easier to say, damn it-- was small for his age, a skinny boy with a shock of black curls that would have been the pride of any Roman mother. Of course, a Roman mother would have them cut and oiled neatly, not left in the mad riot this boy apparently preferred.

He looked like a wildling, and spoke Latin with the same easy fluidity that his brother did. Same soft, rolling accent as well. 

Greg could tell before he'd finished his sentence that this boy was going to be trouble.

"You didn't eat the food they brought you?" He asked instead, and hunkered down to a knee to meet the sulking child's gaze, 

"It's poison."

"It's not! It's bread and garum. Lovely stuff, all the way from Rome."

Sherlock sat up straighter, and pulled a face of disgust as Greg made a show of popping a bite into his mouth. He didn't know what the kid's problem was; it was a damn sight better than the hedgerow nonsense these Celts ate!

Maybe he just didn't have much of a palate, ruined by a lifetime of blackberries and those bleached white carrots they were so fond of.

"It'll serve you right if it makes you sick! It smells like  _ fish _ ."

It didn't seem worth it to mention that it was made of fish. Delicious.

"You know, I've seen your brother. He's worried about you."

Like magic, something flickered across Sherlock's face; something that made him look his age, instead of the brave, defiant mask he'd been wearing. His dirty fingers curled at his sides, half buried in the thick weight of his cloak, and Greg could see the way his throat bobbed tightly.

"What did you do to him? He'll come and get me, you just wait and see! He won't leave me to be sacrificed to your stupid Gods!"

"What?" Greg rocked back on his heels, and tried not to laugh, "You don't look much like a goat to me. And we're not going to kill you! Whatever those idiots might have said." It was a gamble, as he lowered his voice to a conspiratorial tone, and motioned over his shoulder towards some of the other guards.

Sherlock paused, thinking, and finally scurried closer to the bars, "You have to tell him I'm here."

Easier said than done.

How was he supposed to send word to the heir of the Iceni, when the tribe had been-- for all practical purposes, according to the Legate-- wiped out?

It took another two days.

**Ω**

They were the longest two days of Mycroft's life.

For two days he scoured the countryside, and prayed to every God he'd ever heard of. Their clan feared the worst, and his parents were beside themselves with grief. 

When his brother was found-- and it had to be when, not if, because Mycroft couldn't stand the idea of losing Sherlock-- he would try to be a better brother. He would do everything in his limited power to keep him amused, so this never happened again.

On the night of the second day, word finally came.

**Ω**

From the far side of the yard, Greg watched as the Iceni delegation approached the gates. It was the first time he'd seen Mycroft in the daylight, his red hair flaming under the thin winter sunlight. He cut a striking figure in dark furs and deep blue wool, his lean frame flanked on both sides by armed Celtic warriors.

It was hard to believe that this was the same man that had told him about the Morrigan, and the Tuatha dé Danann; and listened to him speak of Heracles, and the many other children of Jupiter. 

At least, it was hard to believe until Sherlock was escorted up to the courtyard, and fled across the cold ground into his brother's arms. Safe at last.

And as the delegation, plus one relieved little boy, made their way back down the hill, Greg slipped out the side gate and hurried after them. It was a spur of the moment decision, his heart beating fast under his breastplate. 

For half a mile he followed, waiting until they were well and truly away from camp before he yelled:

"Mycroft, wait!"

Mycroft stopped and turned, the corners of his mouth curving up faintly. But he waited, his arm and the heavy drape of his cloak still wrapped around his brother's skinny shoulders. "I have you to thank for saving my brother. I hear he gave you quite the trouble."

Sherlock grinned unrepentantly.

"I'm glad he's going back where he belongs. I've been thinking..." Greg swallowed, his mouth dry from more than just exertion. "I've been planning to go back to Rome, but it's maybe not so bad here. And I've got a chance at a promotion soon."

"Yes...?"

"See, I just got it into my head that I might... Stay. If you're going to be leading your people and all, maybe it'd be good for both sides to have some clear heads? And since you and I get on so well..."

And there he was, the man that had flushed at the stories of Jupiter, and told Greg about the Celtic constellations. He was smiling up at him, with red hair and pink cheeks, and Greg knew he wasn't going back to Rome any time soon.

"I'd like that... I'd like that very much."

Come to Britiannia, they said. And for the first time, Greg was very glad he had.


End file.
